This invention relates to a contact structure in which a bump is annexed to a lead extending on an insulative sheet.
U.S. Pat. No. 5,354,205 discloses a probe pad in which a lead and a bump are formed of a single metal by plating growth and the bump is press contacted with an electrode pad of a circuit element to be tested.
The metal of which the bump is formed is required to have durability sufficient to withstand repeated contact and hardness sufficient to break an oxide film on a surface of the electrode pad. As such metal, nickel or nickel alloy is normally used.
On the other hand, the metal of which the lead is formed is required to have excellent conductivity and be comparatively flexible. As such metal, copper or copper alloy is normally used.
In the above-mentioned U.S. Pat. No. 5,354,205, the bump and the lead are formed of the same metal. This involves the problem that if copper or copper alloy which is good for the lead is selected, it cannot satisfy the requirement for the bump and, on the contrary, if nickel or nickel alloy which is good for the bump is selected, cracking is liable to occur when the lead is bent.
It is, therefore, an object of the present invention to provide a contact structure of a lead which is capable of solving the above problem.
Another object of the present invention is to provide a contact structure of a lead in which a bump and a lead are soundly connected together in terms of electricity and strength.
A contact structure according to a first aspect of the present invention includes a lead formed by etching a conductive foil and a bump formed by electric casting by means of plating. The bump and the lead are formed of different metals, respectively.
The bump is connected to a surface of the lead through a conductive connecting material. The lead is intimately contacted at a surface, on which the bump is disposed, with a first main surface of a holeless insulative sheet.
A basal portion of the bump is forcibly pierced into and extended all the way through a material of the holeless insulative sheet and a side surface of the basal portion of the bump is fusion-adhered to an inner wall surface of the through-hole. A distal portion of the bump is projected from a second main surface of the insulative sheet so as to be subjected to press contact with an electrode pad of a given electric part.
A contact structure according to a second aspect of the present invention includes a lead formed by plating and a bump formed by electric casting by means of plating. The bump and the lead are formed of different metals, respectively.
The bump is connected, by plating, to a surface of the lead. The lead is intimately contacted at a surface, on which the bump is disposed, with a first main surface of a holeless insulative sheet.
A basal portion of the bump is forcibly pierced into and extended all the way through the thickness of a material of the holeless insulative sheet and a side surface of the basal portion of the bump is fusion-adhered to an inner wall surface of the through-hole. A distal portion of the bump is projected from a second main surface of the insulative sheet so as to be press contacted with an electrode pad of a given electric part.
A contact structure according to a third aspect of the present invention includes a lead formed by plating and a bump formed by electric casting by means of plating. The bump and the lead are formed of different metals, respectively.
The lead is intimately contacted with and extended on a surface of an insulative sheet, and the bump is connected, by plating, to a surface of the lead.
The bump has a recess formed in the plate-connecting surface and the lead has a protrusion portion connected, by plating, along an inner wall surface of the recess.
A part of the lead connected, by plating, to the bump is embedded in the insulative sheet.